Chair iron



NOV. 14, 1967 ANDERSON 3,352,526

CHAIR IRON 2 Sheets-Sheet 1- Filed Nov. 2, 1965 Nov. 14, 1967 G. A. ANDERSON CHAIR IRON Filed Nov. 2, 1965 2 Sheets-Sheet 2 United States Patent 3,352,526 CHAIR IRON George Albert Anderson, Gardner, Mass., assignor to Collier-Keyworth Company, Gardner, Mass., a corporation of Massachusetts Filed Nov. 2, 1965, Ser. No. 506,079 11 Claims. (Cl. 248-380) ABSTRACT OF THE DISCLOSURE A chair iron for a tiltable chair in which a sheave is position intermediate the pivot of a tilting member and a flexible cable connecting a free end of a spring opposite the springs seat on the tilting member to a fixed anchor. .The sheave has a convex curved surface on which the cable bears which is a greater distance from the pivot at the portion of the surface closest the spring than at the other portion so that the effective length of the cable from its anchor to the end of the spring is gradually shortened as the chair tilts.

This invention relates to a chair iron and more particularly to a chair iron for tilting action in which a spring force is provided to oppose the force causing the tilting action.

In conventional chair irons for use in chairs having tilting seats or backrests, one or more springs is provided to urge the tilting part of the chair iron toward its at-rest horizontal position. However, such irons have been so arranged that the force tending to return the device from its tilted position toward its horizontal position has been approximately directly proportional to the extent of tilting. This characteristic has resulted in chairs which are uncomfortable because of the difiiculty of maintaining a partially tilted position. As the center of gravity of the person seated in the chair moves laterally away from the pivot point during tilting, the torque causing tilting has increased at a faster rate than the restoring force, causing tilting to increase to the maximum extent permitted by the stops. Consequently, it has been difficultfor one sitting in such a chair to attain a stable tilted position intermediate the two extremes.

One object of this invention is to provide a chair iron in which the force opposing tilting action increases at an increasing rate inproportion to the'degree of such action, thereby increasing the safety and ease of operation of such chair irons in their tilted positions.

Another object is to provide a chair iron which facilitates the attainment of a stable position at any desired degree of tilting by one sitting in a chair embodying the present chair iron.

Another object of this invention is to provide such a chair iron in as simple and as inexpensive a construction as possible.

In general, this invention features a sheave member so designed as to increase the restoring or resistant force at an increasing rate as the chair iron is tilted. The sheave is positioned intermediate the pivot of the tilting member and a flexible cable connecting a free end of a spring and a relatively movable member. The sheave has a surface on which the cable bears which is a greater distance from the pivot at one end of the surface than at the other.

Other objects, features and advantages of this invention will be apparent to those skilled in the art from the following detailed description of a preferred embodiment thereof together with the accompanying drawings in which:

FIG. 1 is a view in elevation of a chair iron in accord ance with the invention;

FIG. 2 is a sectional plan view taken along the line 2-2 of FIG. 1;

FIG. 3 is an end view partly in section taken along the line 3-3 of FIG. 1;

FIG. 4 is a sectional elevation taken along the line 4-4 of FIG. 2 showing in broken lines the operation of the chair iron according to the invention; and

FIG. 5 is an exploded isometric view of several of the elements of the chair iron illustrated in FIGS. 1-4.

The illustrated preferred embodiment of this invens tion includes a support member 12 mounted on spindle 10, FIGS. 3 and 5, the lower end of which may be threaded for mounting in the usual way on any conventional chair base. Support member 12 is in two parts, for manufacturing convenience: an external housing member 14 and an internal housing member 18. Housing members 14, 18 are of generally inverted U-shaped configuration, the legs of both members 14 and 18 being of the same terminal configuration, but the legs 19, 20 of internal member 18 being shorter than those 15, 16 of external member 14 and being spaced apart to permit a mating snug fit between them and legs 15, 16 of external member 14. Members 14, 18 are riveted together at 22 with their terminal ends matched and with their parallel bases 17, 21 spaced apart to form an open ended box frame. Spindle 10 extends through the bases of members 14, 13, the spindle being keyed at 26 to the base of member 14.

A tilting member or chair mounting member 28, FIGS. 1, 3 and 5, consisting of generally parallel legs 29, 30 extending from bridge 31, is pivotally mounted at pivots or trunnions 24, 24 provided in the terminal portions of legs 15, 16, 19, 29 of members 14, 18, in position so that bridge 31 extends across one open end of the box frame of support member 12. Adjacent the upper portion of legs 29, 30 of the mounting member 28 are provided holes 32 for fastening a chair seat thereto. A pair of apertures 34, 35 are provided in bridge 31 equidistantly spaced from legs 29, 30 opposite the open end of the box frame, the apertures having outwardly extending peripheral flanges 36, 37 for positioning the ends of compression'springs 38, 39, FIG. 2, which are mountedwith one end thereof 40, 41 abutting bridge 31. Free ends 42, 43, of springs 38, -39 are remote from-bridge 31.

A generally U-shaped cable block or tension yoke 46, FIG. 5, is slidably mounted between bases 17, 21 of support member 12 with its base 48 adjacent the open end of member 12 remote from bridge 31'of member 28 and with its legs straddling spindle 10. A hearing groove 49 extends about base 48 of yoke 46 to receive and support a cable thereabout.

A fixed sheave 50, FIGS. 4 and 5, is secured as at 25 within support member 12 between bridge 31 of mounting member 28 and the legs of yoke 46. Sheave 5i) includes a convex surface 52 curving downwardly away from yoke 46 and having bearing grooves 54, 55 aligned with openings 34, 35 in bridge 31 and with groove 49 of yoke 46.

The curved surface 52 is so arranged that the distance between the pivot axis of member 28 and the upper face of surface 52 increases in the direction toward bridge 31. That is, the distance a, FIG. 4, from pivot 24 to surface 52 or grooves 54, 55 adjacent bridge 31 is greater than the distance b from pivot 24 to surface 52 or grooves 54, 55, adjacent spindle and the distance from pivot 24 to each successive point on surface 52 or grooves 54, 55 is likewise greater in the direction of bridge 31 than is that of the preceding point thereon.

A flexible cable connecting means 56 of predetermined length, FIGS. 2 and 5, extends from the free ends 42, 43 of springs 38, 39 seated on bridge 31 through openings 34, 35 and along sheave grooves 54, 55 and about yoke 46 in groove 49 therein. The ends 57, 58 of cable 56 are enlarged and are fastened to springs 38, 39 by means of spring cap 60 which extends across free ends 42, 43 of springs 38, 39 and which is sloted to receive and hold enlarged ends 57, 58 of cable 56. Detents 63, 64 in cap 60 locate the free ends 42, 43 relative to cap 60 and enlarged ends 57, 58. In the preferred embodiment, a nonextensible nylon-covered steel Wire cable is used.

A tension-adjusting screw 45 having a hand Wheel 44 at one end is threaded through a tapped hole 47 in the base 48 of yoke 46 so that the end of the screw bears against spindle 10. By turning the screw, base 48 of yoke 46 may be moved away from spindle 10, compressing springs 38, 39.

Stop means, FIG. 5, in the form of detents 67, 68 struck from legs 29, 30 of mounting member 28 are also provided to limit the extent of tilt of mounting member 28 with respect to support member 12 by engaging abutments at 25 on legs 15, 16.

When assembled, the pivot point 24 of chair support member 28 is below and slightly to the left of the point at which cable 56 contacts fixed sheave 50, as best appears in FIG. 4.

In operation, the torque tending to return member 28 to horizontal position is determined by the force exerted by springs 38, 39, which is proportional to the extent of compression, and by the length of the moment arm extending from pivot point 24 perpendicular to the direction of the spring force acting on the bridge 31 of the tilting member. Because of the shape of the curved surface of sheave 50 and its relation to pivot point 24, the displacement of the springs 38, 39 increases as the extent of tilt increases and increases at a faster rate. Less cable is available between the opposite ends of the springs than there would be if the cable from the yoke to the bridge were allowed to be rectilinear. Because the effective length of the cable from its anchor to the end of the spring is gradually shortened as the chair tilts, the rate at which the spring is compressed is not a linear function of the extent of tilting; instead the rate of compression acceler ates as the extent of tilt increases. Consequently, the torque tending to restore member 28 to horizontal increases with compression of the springs 38, 39, and increases at an ever greater rate as the extent of tilt increases. To adjust the torque as desired, hand wheel 44 may be manipulated to adjust the compression of springs 38, 39.

Other embodiments of this invention will occur to those skilled in the art which are within the spirit and scope of the appended claims.

What is claimed is:

1. A chair iron comprising:

a support member;

a tilting member pivotally mounted on said support member for tilting movement from an at-rest position with respect thereto;

spring means secured to one of said members;

flexible connecting means connecting said spring means to the other of said members to provide a force applied at a position spaced from said pivot to urge said tilting member to its at-rest position; and

means for increasing said force at an increasing rate as the extent of tilting movement increases including a member having a surface against which said connecting means bears, the spacing between said surface and said pivot increasing in one direction along said surface.

2. The chair iron claimed in claim 1 in which said member having a surface against which said connecting means bears is a sheave having a curved surface.

3. The chair iron claimed in claim 2 in which said connecting means is a cable of predetermined length above and in abutment with said sheave member surface intermediate said spring means and said other member.

4. The chair iron claimed in claim 3 in which said cable and sheave surface are above said pivot.

5. The improvement claimed in claim 4 in which said sheave is mounted on said support member and each successive point on said sheave surface in the direction of tilt is a greater distance from said pivot than each preceding point thereon. a

6. The chair iron claimed in claim 5 in which said spring means is at least one compression spring positioned having one end thereof seated on said one member and having a free end at the other end thereof, said cable connecting said free end to said other member.

7. The chair iron claimed in claim 6 in which said one member is said tilting member adapted to have a chair mounted thereon, said other member is said support mernber, and said free end is the end of said spring means remote from said support member. 8. A chair iron comprising:

a support member adapted for mounting on a substan-,

tially vertical support spindle;

a chair mounting member pivotally mounted at a pivot on said support member for tilting movement adapted to have a chair seat mounted thereon;

a pair of compression spring members generally horizontally positioned each with one end thereof positioned adjacent said chair mounting member and with the other end thereof free;

a tension yoke mounted on said support member stationary relative to said chair mounting member in general horizontal alignment with said spring members, and remote from said free ends;

a flexible cable of predetermined length fastened at said free ends and extending generally horizontally therefrom around saidtension yoke;

a sheave member mounted on said support member stationary relative to said chair mounting member intermediate said cable and said pivot and intermediate the ends of said cable and said tension yoke belgw said cable having a surface in abutment there- Wit said horizontally aligned position being vertically inter mediate said pivot and said chair seat; and

said sheave member having its surface abutting said cable downwardly curved in direction toward said spring members and said surface being spaced from said pivot point a greater distance adjacent said spring members than at the portion of said surface remote from said spring members;

whereby on titling of said tilting member the resistance force to tilting increases at an increasing rate.

9. The chair iron claimed in claim 8 in which said tension yoke is slidably mounted on said support member, said support member is adapted to receive therethrough said spindleintermediate said yoke and said spring members, and said tension yoke includes adjustment means adapted for bearing against said spindle to selectively slide said yoke to adjust the compression of said spring members.

10. The chair iron claimed in claim 9 including stop means on said support member and saidmounting member to limit the extent of said tilting.

11. The chair iron claimed in claim 1 in which said member having a surface against which said connecting means bears is a sheave having a convex surface.

(References on following page) 6 References Cited 2,818,911 1/1958 Syak 248-378 Cramer 1 g 'f i 225 355 JOHN PETO, Primary Examiner.

engp1e Keyworth 5 E. Exammer. 10/1944 Bolens 248380 R. P. SEITTER, Assistant Examiner. 

1. A CHAIR IRON COMPRISING: A SUPPORT MEMBER; A TILTING MEMBER PIVOTALLY MOUNTED ON SAID SUPPORT MEMBER FOR TILTING MOVEMENT FROM AN AT-REST POSITION WITH RESPECT THERETO; SPRING MEANS SECURED TO ONE OF SAID MEMBERS; FLEXIBLE CONNECTING MEANS CONNECTING SAID SPRING MEANS TO THE OTHER OF SAID MEMBERS TO PROVIDE A FORCE TO APPLIED AT A POSITION SPACED FROM SAID PIVOT TO URGE SAID TILTING MEMBER TO ITS AT-REST POSITION; AND MEANS FOR INCREASING SAID FORCE AT AN INCREASING RATE AS THE EXTENT OF TILTING MOVEMENT INCREASES INCLUDING A MEMBER HAVING A SURFACE AGAINST WHICH SAID CONNECTING MEANS BEARS, THE SPACING BETWEEN SAID SURFACE AND SAID PIVOT INCREASING IN ONE DIRECTION ALONG SAID SURFACE. 